The fabric industry, especially the carpet industry, is interested in reducing or preventing the fading of dyed fabrics caused by ozone. By fading is meant loss of fastness of the dye; for example, the dye becomes less bright, changes color, or becomes less appealing. For example, a dark blue dye will change to light blue.
Ozone is an allotropic form of oxygen. The molecule of ozone consists of three atoms of oxygen whereas a molecule of oxygen contains only two atoms of oxygen. Ozone is generally present in the air at concentrations from about 1 to 5 parts per hundred million (pphm).
Ozone is an unstable gas with a pungent odor which decomposes to ordinary oxygen. Ozone possesses a powerful bleaching action and oxidizes substances more rapidly than oxygen and promotes spontaneous ignition of many substances. Its presence in air is known to contribute to the characteristic properties of smog. Embrittlement of rubber compounds is accelerated by the presence of traces of ozone in the air.
Ozone is formed in the upper atmosphere by the action of high energy radiation from the sun splitting oxygen molecules into two oxygen atoms. These atoms then combine with oxygen molecules to form ozones (O.sub.3). Under conditions of heavy smog, where sunlight acts on a combination of unburned hydrocarbons from gasoline and oxides of nitrogen, the concentration has been known to exceed 10 parts per hundred million. However, even at low ozone concentrations, if the humidity is high enough, ozone fading is known to occur. In addition, ozone can be produced through the electronic irradiation of air or oxygen such as that experienced in the presence of electric motors and electronic devices.
Ozone is an electrophillic reagent, that is it searches out and attacks electron pairs such as those existing in carbon-carbon double bonds. Dyes have a multiplicity of double bonds and perhaps for this reason are sensitive to ozone. The dyes which are attacked are usually anthraquinone type dispersed dyes; although, it is believed that under severe conditions, almost all dyes will be affected by ozone. The dyes in a synthetic fiber such as nylon are most seriously attacked when the dyes are mobile in the synthetic fiber. Cationic dyes are also susceptible. The most sensitive dispersed dyes are usually blue anthraquinone type dyes.
High humidity enhances the noticeable ozone fading. Apparently, moisture provides the dye sufficient mobility to diffuse to the surface of the yarn where the destruction of the dye occurs.
Ozone fading can be decreased by reduction of the specific surface area of the yarn. Ozone fading can also be decreased by changes in polymer morphology and orientation but these techniques are inherently expensive.
A number of chemicals have been called antiozonants in the literature which protect rubber from ozone. Examples are the para-phenylenediamine derivatives and the dihydroquinoline derivatives. In nylon and other synthetic fibers these chemicals seriously discolor the yarn especially after exposure to light thereby severely limiting the use of such chemicals.
U.S. Pat. No. 3,822,996 discloses and claims a method for improving fastness of dyes in fibers dyed with anthraquinone dyes. The method consists of coating said dyed fiber with a compound selected from the group consisting if thiourea and a saturated alkyl substituted thiourea so that from about 0.2 to about 5% on weight of the fiber of said compound remains on said fiber. This patent claims to reduce the ozone degradation of the dye through the use of these water soluble thioureas.
U.S. Pat. No. 3,844,713 discloses alkyl and aryl phosphites useful in inhibiting ozone fading of dyed polyamides. This patent discloses that when from about 0.7% to about 3% of organic phosphites are coated on nylon fiber or are added to the polymer prior to spinning, improved dye fastness is achieved when compared to an untreated dyed nylon fiber.
U.S. Pat. No. 3,859,045 discloses the use of ethoxylated aliphatic tertiary amines to reduce ozone attack on dyes in polyamide fibers. Specifically, this patent is concerned with the use of about 0.1% to about 8% of tertiary amines such as N,N-bis-(2-hydroxyethyl)-2-aminooctadecane. This patent discloses that from about 0.1 to about 8% on weight of fiber of the compounds disclosed will reduce the fading of dyed polycarbonamide fabrics.
U.S. Pat. No. 4,304,568 discloses a method for minimizing ozone fading in dyed polyamides by treating the dyed polyamide with a substituted piperidine thiourea.
U.S. Pat. No. 4,613,334 describes a process for improving the light fastness of dyeings obtained with acid dyes and/or metal complex dyes on polyamide textile materials, by treating the textile with a copper hydroxamate before, during or after dyeing.
U.S. Pat. No. 4,631,066 discloses that light resistant aromatic polyamide fibers can be improved by heat treating the aromatic polyamide fibers in the presence of urea and thiourea.
None of these patents suggest or disclose the use of compounds such as oxadiazine-4-thiones and triazinethiones to prevent ozone degradation of dyes.